Drunk driving is something that's already illegal (obviously), and the bac threshold is quite low here, although I do wish it was (much) more stringently enforced.
You can't throw law enforcement at a problem when it itself is a problem in a lot of cases.
Hey, you don't have to tell me, I'm still waiting for smoke-free bars. Underage drinking is enforced even less than that, but it's a much less widespread problem.
The lack of "on-premises" laws is especially of little concern, as we very rarely get public disturbances because of drunk people.
To be fair though I'm witnessing a shift the last few years, at least in restaurants/tavernas/fast-food joints. You can more easily find places to eat these days where smoking inside is not allowed.
They don't. Some people even at 20s, 30s, 40s, haven't had the necessary mental/emotional development.
That's not correct. The law states clearly that alcohol purchase and consumption in public are illegal for underage people [1]. It's also illegal to enter premises where alcohol is served, without being escorted by an adult. Unfortunately the problem with Greece is not the lack of laws, it's enforcing them
[1] https://www.taxheaven.gr/laws/law/index/law/213 (in greek)